The majority of plants obtain most of their nutritional requirements from the plant medium in which they are growing. The plant growth medium, is characterized by its capacity to exchange ions. Plant roots derive their nutrients from the growth medium by the exchange of nutrient ions within the medium to sites on the roots of the plants. In the absence of an aqueous transfer medium, i.e., moisture, plants have not been able to grow well or even survive.
Agriculturalists and agronomists have to work with all types of plant growth media such as sand, natural earth, horticultural soils, and various soil-mimicking, soil-less plant culture substrates, all of which will be generically referred to hereinafter as soil; however, the bane of essentially all who work in the field is water repellent soil (WRS). Water repellent soil retards water infiltration into the soil matrix; often exists as local dry spots (LDS); and can render entire areas of the upper layers of the soil substrate essentially impervious to water penetration. Under rainfall or irrigation conditions, dire environmental consequences can result from the water repellency of the soil, such as surface runoff or leaching into pristine areas and/or potable reservoirs, of water and aqueous compositions containing pesticides and/or fertilizers.
A characteristic of soils, especially field soils, is that during a dry period, i.e., a period of days or weeks with very little to no rain, the moisture content of the soil can reach a very low level at which point the soil becomes unable to be re-wetted by the application of water via rain or irrigation alone and thus the soil becomes no longer an acceptable plant growth medium. It is understood by those in the art that the soil has dropped below the Critical Water Content (CWC).
Water repellency of a soil is not only a function of the initial water content of the soil, but is also a function of soil particle size, e.g., sands are more prone to water repellency than clays, as well as the type of organic matter incorporated in the soil. This organic matter induces water repellency in the soils in various ways, such as by providing hydrophobic organic substances leached from plant litter; organic substances that have been irreversibly dried; and/or hydrophobic microbial by-products.
Before water will evenly infiltrate into or percolate through a soil matrix, there must be a continuous film of water on the soil particles. In other words, the soil must first be wetted before water will flow through it. Agriculturalists have realized that the Critical Water Content level can be modified and the water repellency of these soils can be reduced through the use of wetting agent surfactant compositions; especially compositions containing nonionic surfactants. However, the degree of efficacy among surfactant chemistries and formulations has varied significantly. To ameliorate water repellency and/or to enhance infiltration, high rates of wetting agents are frequently applied; such elevated rates may become injurious to plants. For example, the surfactants being utilized to increase the moisture levels in soil tend to not penetrate deeply into the soil, i.e., they remain in the upper regions of the soil and biodegrade rapidly thus requiring numerous applications. Furthermore, the increase in concentration of the surfactants currently deemed necessary in initially water repellent soil often have a severe, negative impact on the surrounding environment, especially toxicity to plant tissues, and have a negative effect on the plant growth properties of the soil.
“Although an increasing number of researchers are aware of the occurrence and consequences of water repellency in a wide range of soils, it is still a neglected field in soil science.” (Dekker et al., International Turfgrass Society Research Journal, Volume 9, 2001, pages 498-505)
Agriculturalists continue to seek a composition which, when applied to a plant growth medium susceptible to unacceptable drying, would i) rapidly and uniformly penetrate deeply into the medium matrix; ii) enable significant re-wetting of the medium, i.e., modify the Critical Water Content especially around the plant rootzone; iii) provide a long lasting effect to reduce the necessity for frequent applications; and iv) be effective at lower concentration levels than surfactants currently being used, thus reducing the negative impacts that any chemicals can have on the environment.
The instant invention provides the above-enumerated advantages and, serendipitously, enhances plant growth, especially plant density, color, and quality without the need for fertilizer applications.